Abstract Acne is an important human skin disorder and is thought to be caused by skin commensal P. acnes. We have identified two types of hyaluronidases, made by P. acnes, that are either pro or anti- inflammatory. Human colonization by P. acnes that encodes the pro-inflammatory hyaluronidase appears to be associated with development of moderate acne, and conversely colonization with P. acnes that encodes the anti-inflammatory hyaluronidase is associated with healthy skin. Based on our findings, we propose that hyaluronidases play a role in acne by affecting the pro-inflammatory potential of P. acnes strains. For Aim 1, we propose to study the pathogenic mechanisms of both hyaluronidases in murine models of acne. For Aim 2, we further seek to investigate the association between hyaluronidase type and acne-genic potential using one of the best characterized collection of P. acnes strains, from individuals with or without acne.